1. Field of the Invention
The present invention relates to a controlling method for operation of a painting booth wherein objects carried continuously therethrough are painted.
2. Description of the Prior Art
For spraying a paint on a body of cars, for example, the prior art comprises an elongated painting booth having a tunnel-like painting chamber, wherein a conveyor for carrying the body thereon is laid, and a plurality of painting machines are disposed in the direction of conveyance, thereby spraying a paint on the body flowing on the conveyor at regular intervals through the painting machines properly selected therefor.
In such a continuous painting, however, it is essential for enhancing a paint quality that a paint mist arising from spray and an evaporating organic solvent be removed quickly from within the painting chamber, and thus the painting booth is structured generally such that the painting chamber is provided with an air inlet chamber and an exhaust chamber at upper portion and lower portion respectively, thereby generating a vertical current of a conditioned air within the painting chamber. In such painting booth, the aforementioned paint mist and evaporating organic solvent are quickly discharged outside the painting chamber on the vertical air current, and the painting chamber is kept at a constant atmosphere inside.
However, a large-sized painting booth may range 90m or over in full length, and in all such large-sized booths, the problem is such that it is very difficult to control the atmosphere in the painting chamber uniformly. Such being the circumstances, there developed recently is a painting booth to a practical service which is constructed to have the painting chamber divided inside into a plural zone longitudinally, independent air inlet and exhaust systems being connected to each zone to a fine control of the atmosphere.
Meanwhile, in the case of large-sized painting booth divided into a plurality of zones as mentioned above, there appears a zone where the object to be painted is not present, or such a zone as is not concerned in painting for a while after the operation starts or before the operation is over. Accordingly, an advantageous operation may be secured in the point particularly of energy saving from an arrangement wherein air inlet and exhaust systems of each zone will be actuated or shut down independently according to a state where the object to be painted is carried, that is. air inlet and exhaust systems will be actuated successively from a zone wherein the object to be painted arrives and shut down successively from a zone wherein the object to be painted is not present. However, in the aforementioned painting booth prevailing hitherto, if air inlet and exhaust systems are actuated or shut down per zone, a horizontal air current is generated in the painting booth, and thus a defective painting may result from the paint mist sticking on the surface of the object to be painted in a zone where the painting is under way.
Now, therefore, according to Japanese Patent Laid-Open No. 165062/1982, the painting booth itself is subjected to improvement, thereby ensuring an operating method so as not to generate a horizontal air current. The painting booth is shaped like a tunnel, as shown in FIG. 1, with air inlet chambers 1a, 1b and exhaust chambers 2a, 2b formed at upper and lower portions respectively. Dividers 4, 4, 4 are formed from the air inlet chambers 1a, 1b toward the exhaust chambers 2a, 2b in a painting chamber 3 and also at accesses vertically, and closable doors 6a, 6b, 6c are at every dividers 4 so as to allow a car body 5 as an object to be painted to pass therethrough. Then, air conditioners 8a, 8b are mounted for the air inlet chambers 1a, 1b through blast fans 7a, 7b, exhaust fans 9a, 9b are mounted for the exhaust chambers 2a, 2b, and further damper like pressure regulators 10a, 10b for regulating internal pressures are mounted on an inside wall of the painting chamber 3.
Thus, when the painting chamber 3 is started for operation, first the doors 6a, 6b, 6c are kept close, the blast fan 7a and the exhaust fan 9a are actuated, and also the pressure regulator 10a is actuated, thereby generating a vertical air current in a zone A. The door 6a is opened in the stage where the car body 5 comes near to the zone A, and thus the car body 5 is allowed to come into the zone A to painting. Then in the stage where painting on the car body 5 properly goes in the zone A, the blast fan 7b and the exhaust fan 9b are actuated, and also the pressure regulator 10b is actuated, thereby generating a vertical air current in a zone B. Then in the stage where the car body 5 comes near to the zone B, the doors 6b, 6c are opened, the car body 5 is thus allowed to come into the zone B to painting. After the painting in the zone B is over, the car body 5 is carried outside the painting chamber 3, and then car bodies on the second and thereafter are subjected to painting with all the doors 6a, 6b, 6c kept open.
At the time when the painting booth is stopped for operation, the doors 6a, 6b are closed in the stage where the final car body 5 leaves the zone A, and the blast fan 7a and the exhaust fan 9a are shut down at the same time. Then in the stage where the final car body 5 leaves the zone B, the door 6c is closed and the blast fan 7b and the exhaust fan 9b are shut down.
However, according to the method disclosed in the aforementioned Japanese Patent Laid-Open No. 165062/1982, it is difficult practically to find a time to operate the doors 6a, 6b, 6c, and numerous parts are required to complicate the structure.
On the other hand, in the large-sized painting booth divided into a plurality of zones as described, the problem is such that a defective painting is easy to arise among objects to be painted even in a steady operating state free from the aforementioned sequential start-up and shutdown. Upon closer examination by the inventors, it has been clarified that there is generated a horizontal air current in both the zones A, B other than the vertical air current, and the combined air current flows slantwise to scatter the paint mist. To prevent the defective painting, the horizontal air current must be kept from arising, however, in the prior art painting booth, merely a feed air quantity is adjusted, and a measure for restraining the horizontal air current is not particularly taken, therefore the aforementioned defect cannot be avoided.